Strawberries are perennial plants that typically remain productive for three to five years. Protecting them from harsh winter conditions is key to ensuring a bountiful harvest the following spring. This process involves an annual cycle of renovation, conditioning, and protection that prepares the plant crown for cold temperatures. By managing this cycle, home gardeners can successfully save their strawberry plants year after year.
Post-Harvest Renovation and Thinning
Immediately following the final harvest in summer, the strawberry patch requires intensive renovation to set the stage for next year’s growth. This step is important because strawberry plants form the flower buds for the following season during late summer and early fall. Neglecting this care can result in reduced yields.
The first step is to cut back the foliage, often called “mowing” in large beds, reducing the leaves to one to two inches above the crowns. This trimming removes old, diseased, or damaged leaves, stimulating fresh new growth and improving air circulation. For smaller patches, hand shears or hedge clippers accomplish this goal without risking damage to the central crown.
Renovation must also address overcrowding caused by mother plants sending out runners and daughter plants. Dense patches compete for water and nutrients, resulting in smaller berries and increased disease susceptibility. Thinning involves removing older, less productive mother plants and excess runners. Leave the healthiest plants spaced approximately 4 to 6 inches apart within the row. After thinning, apply a balanced fertilizer and thoroughly weed to replenish soil nutrients and encourage vigorous growth for flower bud formation before winter.
Preparing Plants for Dormancy
As summer transitions into fall, the focus shifts to conditioning the plants for dormancy. This transition is signaled by cooling temperatures, which causes the plants to “harden off.” Hardening off is a physiological process where the plant accumulates sugars and reduces water content, increasing tolerance to freezing temperatures.
Gradually reduce watering frequency during this time, especially if rainfall is adequate, to prevent lush growth susceptible to cold damage. The first few light frosts, where temperatures dip just below freezing, act as a natural trigger signaling deep dormancy. The foliage of hardened plants will often flatten out and take on a slightly reddish or bronzed hue as they prepare for the cold.
Preparation for containerized strawberry plants is similar, but the containers require specific management. Plants should remain outdoors to experience the necessary cool temperatures for hardening off. They can be moved closer to a building or sheltered area to shield them from severe weather fluctuations. This allows them to sense the change in seasons without the risk of an untimely freeze-thaw cycle damaging the roots.
Essential Winter Protection
The primary method for saving strawberry plants over winter is providing a thick layer of insulation to protect the crowns from extreme cold and soil heaving. The most damaging condition is the repeated cycle of freezing and thawing, which physically pushes the crowns out of the soil, exposing the roots.
Timing the application of winter mulch is important, as applying it too early can delay dormancy and make the plants vulnerable. Apply insulation only after the plants are fully dormant, typically after the ground has frozen slightly or temperatures have consistently dropped into the low 20s Fahrenheit (-6°C). Lightweight, loose, and weed-free materials are the best choices because they insulate effectively without compacting or smothering the crowns.
Spread the mulch loosely over the entire patch to a depth of four to six inches; this will settle over winter to provide a dense protective layer. Containerized plants require more comprehensive protection because their roots are exposed to cold air on all sides. Place these containers in an unheated garage, shed, or cold frame where temperatures remain cold but stable. Insulate them by wrapping the pot in burlap or placing them completely under a six to eight-inch layer of straw.
Spring Thaw and Early Season Care
As winter recedes, gradually remove the protective mulch to avoid damage from late frosts. Keep the mulch in place as long as possible to delay new growth until the threat of a hard freeze has passed. Open strawberry flowers are highly susceptible to damage at temperatures of 32°F or below.
Monitor the plants and remove the protective layer when the first signs of white or yellowish new growth are visible on about 25 percent of the crowns. Carefully rake the mulch off the crowns and move it into the pathways between the rows. There, it serves as a weed suppressor and keeps developing berries clean. Keeping the removed straw nearby is practical, as it can be quickly pulled back over the plants if a late-season frost is predicted.
In early spring, before active growth begins, thorough weeding is beneficial. Strawberries are poor competitors, and their shallow roots are easily damaged by later cultivation. Established June-bearing varieties do not require a spring fertilizer application, as this encourages leafy growth at the expense of fruit production. Their main feeding should have occurred during post-harvest renovation. Water the plants as needed to ensure consistent moisture as they emerge from dormancy and prepare for the new season.